There is radial movement of pigment granules in normal light adapted eyes of both the butterfly (Pieris brassicae) and moth (Philosamia ricini) whereas in the dark adapted state, there is peripheral distribution of the pigment granules. However all parts of retina do not respond equally. Further, treatment with 5-hydroxytryptamine, cyclic AMP and colchicine completely reverses the movement pattern of the pigments exhibiting a migration pattern similar to a light adapted state. This is thought to be due to dopamine release that acts as a secondary messenger in addition to affecting the microtubules. Similarly, the brain of dark adapted insects shows a large accumulation of neurosecretory material in the form of compact granules, whereas light adapted insects show a significant reduction.